Term
| path of cardiac conduction |
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Definition
- electrical impulses leave SA node
- travel to right and left atria, causing them to contract together
- now a natural delay to allow the atria to contract and the ventricles to fill with blood.
- electrical impulse has now traveled to the AV nose
- electrical impulse now goes to the Bundle of His
- then divides into the right and left bundle branches
- rapidly spreads using Purkinje fibers to the muscles of the right and left ventricle, causing them to contract at the same time. |
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Term
| the 2 parts of the autonomic nervous system |
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Definition
Any of the electrical tissue in the heart has the ability to be a pacemaker. However, the SA node generates an electric impulse faster than the other tissue so it is normally in control. If the SA node should fail, the other parts of the electrical system can take over, although usually at a slower rate.
Although the pacemaker cells create the electrical impulse that causes the heart to beat, other nerves can change the rate at which the pacemaker cells fire and the how strongly the heart contracts. These nerves are part of the autonomic nervous system. The autonomic nervous system has two parts - The sympathetic nervous system and the parasympathetic nervous system. The sympathetic nerves increase the heart rate and increase the force of contraction. The parasympathetic nerves do the opposite. |
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Definition
coincides with the spread of electrical activity over the atria and the beginning of its contraction
-first deflection
- represents excitation (depolarization) of the atria |
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Term
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Definition
coincides with the spread of electrical activity over the ventricles and the beginning of its contraction.
-results from excitation of the ventricles |
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Definition
| coincides with the recovery (repolarization) phase of the ventricles. |
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Term
| Where does the first heart sound ("lub") come from? |
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Definition
| The first heart sound (lub) is caused by the acceleration and deceleration of blood and a vibration of the heart at the time of the closure of the tricuspid and mitral valves |
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Term
| Where does the 2nd heart sound ("dub") come from? |
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Definition
| The second heart sound (dub) is caused by the same acceleration and deceleration of blood and vibrations at the time of closure of the pulmonic and aortic valves. |
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Definition
| Represents ventricular depolarization and repolarization |
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Term
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Definition
| Represents conduction through the atrio-ventricular valve |
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Term
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Definition
| Represents the end of the ventricular depolarization to the onset of ventricular repolarization |
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Term
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Definition
| Common Cardiac Rhythms Normal Sinus Rhythm Sinus Bradycardia Sinus Tachycardia Atrial Fibrillation Ventricular Premature Contractions Ventricular Tachycardia Ventricular Fibrillation Ventricular Asystole |
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Term
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Definition
Normal Sinus Rhythm = 70 – 160 beats / min in the adult dog
This is a tracing of a normal heart rate and rhythm - there is a clear delineation of the P, QRS, and T waves. The heart rate in this tracing is approximately 120 beats per min. Sinus rhythm means that the electrical impulse is originating in the sinus node (sinoatrial node) then spreads to the atria, to the AV node, and then to the ventricles In some animals, you may see a slight variation in the heart rate on an ECG which is related to the respiration cycle - the heart rate increases with inspiration and decreases with expiration – this is a normal finding in many animals. |
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Term
| Sinus Rhythm but with abnormal heart rates |
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Definition
Sinus Rhythm but with abnormal heart rates
The electrical impulse originates in the sinoatrial node then travels the normal pathway. However, the heart rates in these two examples are abnormal.
Sinus Bradycardia = Regular sinus rhythm with a heart rate less than 70 beats/min
Sinus Tachycardia = Regular sinus rhythm with a HR above 160 beats/min |
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Term
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Definition
Atrial Fibrillation
“P” Waves are replaced by several “F” waves
Atrial and ventricular rates are rapid and irregular.
On auscultation, this rhythm sounds like the sound of “jungle drums” where the heart beats are very irregular / uncoordinated.
Cardiac output is decreased
Causes: Most often associated with severe underlying heart disease – The 2 most common conditions are Chronic AV valvular insufficiency and Dilated Cardiomyopathy. Also seen with congenital heart defects, drug reactions, anesthesia, heartworm disease, trauma |
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Term
| Ventricular Premature Contractions / Complex |
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Definition
Ventricular Premature Contractions / Complex
The electrical impulse originates in the ventricles instead of the sinoatrial node
Wide and bizarre QRS complexes
The most frequent type of abnormal rhythm in dogs.
Causes: Cardiac, hypoxia, anemia, uremia, pyometra, GDV, pancreatitis, parvovirus, drugs.
While there are numerous causes of VPCs, they may also occur in normal hearts with no apparent cause. |
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Term
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Definition
Ventricular Tachycardia
V – tach may be intermittent or persistent and consists of 3 or more VPCs in a row
The most serious of all tachyarrhythmias
Causes: Cardiac, hypoxia, anemia, uremia, pyometra, GDV, pancreatitis, parvovirus, drugs. The same as for VPCs but V-tach is often associated with more serious underlying cardiac disease |
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Term
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Definition
Ventricular Fibrillation
Completely irregular, chaotic and deformed reflections of varying width/amplitude/shape
Weak and uncoordinated ventricular contractions which results in decreased to zero cardiac output. Therefore, you will not be able to palpate a peripheral pulse in a severe case.
V-fib causes cardiac arrest
Causes: Cardiac surgery / damage / aortic stenosis, shock, hypokalemia, hypocalcemia, alkalosis, electrical shock, hypothermia, drug reactions |
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Definition
Ventricular Asystole
Flat Line = Cardiac Arrest This is the absence of ventricular contractions (Systole is the part of the cardiac cycle where the heart muscle is contracting. The prefix “a” means without or no.)
Because the heart muscles are not contracting, you will feel no peripheral pulse |
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Term
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Definition
| a group of specialized cardiac muscle cells in the wall of the right atrium of the heart that act as the heart’s pacemaker. The impulse that starts each heartbeat is initiated in the SA node |
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Term
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Definition
| The atrioventricular node (abbreviated AV node) is a part of the electrical control system of the heart that coordinates the top of the heart. It electrically connects atrial and ventricular chambers.[1] The AV node is an area of specialized tissue between the atria and the ventricles of the heart, specifically in the posteroinferior region of the interatrial septum near the opening of the coronary sinus, which conducts the normal electrical impulse from the atria to the ventricles. |
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Term
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Definition
| The bundle of His, known as the AV bundle or atrioventricular bundle, is a collection of heart muscle cells specialized for electrical conduction that transmits the electrical impulses from the AV node (located between the atria and the ventricles) to the point of the apex of the fascicular branches. The fascicular branches then lead to the Purkinje fibers which provide electrical conduction to the ventricles, causing the cardiac muscle of the ventricles to contract at a paced interval |
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Term
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Definition
| The bundle of His branches into the three bundle branches: the right, left anterior and left posterior bundle branches that run along the interventricular septum. The bundles give rise to thin filaments known as Purkinje fibers. These fibers distribute the impulse to the ventricular muscle. Together, the bundle branches and Purkinje network comprise the ventricular conduction system. |
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Term
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Definition
| Purkinje fibers' (Purkyne tissue or Subendocardial branches) are located in the inner ventricular walls of the heart, just beneath the endocardium. These fibers are specialized myocardial fibers that conduct an electrical stimulus or impulse that enables the heart to contract in a coordinated fashion |
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Term
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Definition
| loss of weight, muscle atrophy, fatigue, weakness, and significant loss of appetite, general physical wasting and malnutrition usually associated with chronic disease |
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